Is it really compact or has it just dried out? Materials in potting mix become hydrophobobic when they dry out, and that can cause it to harden. Using a wetting agent helps the water permeate the mix. Sometimes you see it listed in the ingredients of the potting mix, e.g. yucca extract.
Breaking up the top layer, moving dirt around is not really going to help... it's like rototilling hard-pan soil; before long it is back to its 'compact' state.